Low manoeuvreability aircraft like UAVs can be remotely controlled or fly autonomously based on pre-programmed flight plans or having more complex dynamic automation systems. UAVs are currently used in a number of military roles, including reconnaissance and attack. They are also used in a small but growing number of civil applications such as fire fighting where a human observer would be at risk, police observation of civil disturbances and crime scenes, and reconnaissance support in natural disasters. UAVs are often preferred for missions that are too “dull, dirty, or dangerous” for manned aircraft.
There is a general desire and requirement that UAVs, in particular civil UAVs, operate safely and do not collide into other UAVs or other aircraft or objects. It is therefore an object of the present invention to provide a system for avoiding the UAV to collide with another object.
For a collision threat sense and avoidance system (sense & avoid system) to actually perform the avoid portion, an aircraft involved must at some point make an avoidance manoeuvre in order to quickly leave the trajectory having a high sensed and/or calculated risk of collision.
In a case where the system utilizes a last instant manoeuvre, i.e., a manoeuvre that is not performed until the very last instant to avoid collision, such manoeuvre must use the maximum safe manoeuvre capability available to the aircraft. For high performance aircraft, there is usually enough manoeuvre performance available to obtain sufficient path curvature by a so called roll-and-pull manoeuvre, in order to quickly leave the trajectory having the sensed and/or calculated risk of collision
However, for contemporary UAVs, the manoeuvre performance is generally very poor. In fact, the capabilities are commonly poorer than would be acceptable in a manned aircraft.
Also for other low or medium performance aircraft, manned or not, manoeuvre performance is poor.
One of the functions of a sense & avoid system is to select a suitable manoeuvre to be performed in a case of a potential collision. Such a function may be realised by a manoeuvre generator. For some existing types of system the selection of manoeuvre is limited, e.g. only using pure climb or sink, but typically a high performance sense and avoid system must be able to select a multitude of manoeuvres.
For a high manoeuvreability aircraft, a manoeuvre generator can select the roll-and-pull manoeuvre, since this manoeuvre will adequately fulfill the above requirements. For a low manoeuvreability aircraft however, the manoeuvre generator must operate in some other manner.
US 2007/0210953 discloses an aircraft collision sense and avoidance system and method for UAVs. The system comprises among other things an image sensor connected to a target detection unit further connected to a threat assessment unit for assessing the threat of a target detected in the image provided by the sensor by the target detection unit. An avoidance manoeuvre unit connected to the threat assessment unit provides flight control and guidance with a manoeuvre to avoid any identified collision threat.
U.S. Pat. No. 6,510,388 disclose a system and a method for avoidance of collision between vehicles, wherein a possible avoidance manoeuvre trajectory for the respective vehicle is calculated and compared with the avoidance manoeuvre trajectories calculated for the other vehicles for controlling whether the avoidance manoeuvre trajectory of the vehicle in every moment during its calculated lapse is located at a stipulated or predetermined minimum distance from the avoidance manoeuvre trajectories of the other vehicles. Further, it discloses a method of obtaining suitable avoidance manoeuvre directions for two aircrafts, each provided with the system, and with a communications link between them.